I am running an Ignition 7.2.5 server connected to a single AB ControlLogix PLC.
After running fine for a few weeks, the OPC server recently stopped working, showing “No data available” or “Not connected” for the tags it is reading off the PLC.
I reason it is an OPC server problem because the PLC is still operating. Also, if I restart the OPC-UA module from the Ignition Gateway webpage, the problem is resolved.
This most recent incident has happened around the same time as a power interruption. The server that Ignition is running on is on UPS, but not the PLC, so that may have gone offline. I have a 60s timeout alarm set for a 30s heartbeat signal coming from the PLC and looking back through the records, it seems like it has also triggered several times over the past month, most of those times coming back online within a minute or two. This suggests that there may have been several power interruptions, however the OPC connection has remained working after those other events.
I had assumed that the OPC connection to the PLC would simply be re-established when it comes back online after a power interruption. Is it possible that the Ignition OPC-UA server will not be able to manage it if this happens too frequently?
If not, what else might cause this problem?